Add support for additional arguments to load_ui

[bpabel]

Per the python mailing list discussion, add support for the 2nd argument to uic.loadUi

Here is an example using PyQt4

http://nullege.com/codes/search/PyQt4.uic.loadUi

Here is an example of an implementation for PySide that accepts the same arguments

https://gist.github.com/cpbotha/1b42a20c8f3eb9bb7cb8

[mottosso]

Thanks @bpabel.

Per the python mailing list discussion

Would it be possible to link to this discussion?

Here is an example of an implementation for PySide that accepts the same arguments

Excellent, would you happen to know whether the same implementation works for PySide2? If you put a pull-request in, we could have it run through tests on each platform, Python version and Qt distribution. That should get the conversation started.

As I'm not a user of loadUi myself, it would also be lovely to have one or more usage examples so that we implement it in a way that makes sense to you.

[fredrikaverpil]

Would it be possible to link to this discussion?

This was from the closed 3DPRO mailing list. I asked Abel to post an issue :)
@mottosso Did you get my invite?

Excellent, would you happen to know whether the same implementation works for PySide2?

I've made a gist where this works in PySide2:
https://gist.github.com/fredrikaverpil/0a89b174c9d29bc585f11d250adf2a7c

I think Abel's request makes a lot of sense. I omitted additional arguments to the load_ui convenience function but the gist seems to show a clear way to support that. We should do it!

[mottosso]

Would it be possible to post a minimal example ui file, along with how it is used today, and how you would like it to be used with this feature?

[fredrikaverpil]

Would it be possible to post a minimal example ui file, along with how it is used today, and how you would like it to be used with this feature?

I could do a PR, but I won't have time for it until mid August 😢 as I'm on vacation with my family 😄

However, here's an example UI file which we could use for this example. Today, we can access the widgets from the ui file like this:

import sys
from Qt import QtWidgets
from Qt import load_ui


class Hello(QtWidgets.QWidget):
    def __init__(self):
        super(Hello, self).__init__()
        self.ui = load_ui('main_window.ui')

        print(self.ui.boilerPushButton)  # a pushButton widget from main_window.ui

app = QtWidgets.QApplication(sys.argv)
window = Hello()
window.ui.show()
sys.exit(app.exec_())

However, we can't load the UI widgets directly into self and make the pushButton available like this: self.boilerPushButton. So let's say you load three UI files and want all of their widgets to be accessed like self.widgetName. Today this is possible in PyQt (by providing a second argument to uic.loadUi which load_ui wraps) but not in PySide (not without pysideuic). But with @bpabel's gist, this seems doable with a custom QUiLoader class (really nice since it doesn't require the pysideuic module which isn't always available, e.g. missing in Nuke).

Here's a full example of me loading two UIs with the current behaviour of load_ui and it shows how you need to load each UI into separate objects:
https://github.com/fredrikaverpil/pyvfx-boilerplate/blob/master/boilerplate.py#L164-L165

This is what we want to be able to do with an optional second argument to load_ui. So instead of the example above, we could do this:

class Hello(QtWidgets.QWidget):
    def __init__(self):
        super(Hello, self).__init__()
        self.ui = load_ui('main_window.ui', self)  # Load widgets into self

        print(self.boilerPushButton)  # the button is now available in self

Of course, you could also load widgets into something else than just self. The point is you want control on where your UI file's widget ends up being accessible from.

@mottosso if you like, we can assign this to me, but I won't have time for it until a couple of weeks away.

It would basically entail updating pyside_load_ui, pyside2_load_ui, pyqt4_load_ui and pyqt5_load_ui to support this optional argument.

[fredrikaverpil]

Sorry, I edited my prevous post a lot to clarify things a bit with better examples. Please re-read it if you already read it.

[fredrikaverpil]

If we were to write tests for this, we'd need to store a .ui file in the repository. How do you feel about that, @mottosso ?

We could create a main_window.ui file in a data dir?

[mottosso]

We could, but I'd rather keep it contained in the test module.

If you hand me a .ui snippet, I can show you how I mean.

[fredrikaverpil]

If you hand me a .ui snippet, I can show you how I mean.

Will this do?

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralwidget">
   <layout class="QGridLayout" name="gridLayout">
    <item row="0" column="0">
     <widget class="QPushButton" name="pushButton">
      <property name="text">
       <string>PushButton</string>
      </property>
     </widget>
    </item>
   </layout>
  </widget>
  <widget class="QMenuBar" name="menubar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>125</width>
     <height>22</height>
    </rect>
   </property>
  </widget>
  <widget class="QStatusBar" name="statusbar"/>
 </widget>
 <resources/>
 <connections/>
</ui>

[mottosso]

Here's what I had in mind.

def test_pyside_load_ui():
    """load_ui works well"""

    ui = """\
<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralwidget">
   <layout class="QGridLayout" name="gridLayout">
    <item row="0" column="0">
     <widget class="QPushButton" name="pushButton">
      <property name="text">
       <string>PushButton</string>
      </property>
     </widget>
    </item>
   </layout>
  </widget>
  <widget class="QMenuBar" name="menubar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>125</width>
     <height>22</height>
    </rect>
   </property>
  </widget>
  <widget class="QStatusBar" name="statusbar"/>
 </widget>
 <resources/>
 <connections/>
</ui>"""

    with tempfile.NamedTemporaryFile(suffix=".ui") as f:
        f.write(ui)
        f.seek(0)

        with pyside():
            import Qt
            widget = Qt.load_ui(f.name)

Ideally then, the .ui file would only contain parts we are actually testing. In this case, perhaps QStatusBar and explicit widths are less important in the interest of readability.

[fredrikaverpil]

Ah, yes. That's an excellent idea.

[mottosso]

It might not seem like a big deal today. From experience with maintaining external files with tests, I find that this works fine initially, but then as the project is updated, tests change, and the external files will need to branch out to cover both in order to be backwards compatible.

With this approach, even though it makes each test bigger and more repetitive, tests and data change together and should be easier to maintain long-term.

[fredrikaverpil]

Yep. Agreed.

[fredrikaverpil]

Hm, so I'm wondering about one thing. It looks like we could add a custom class to the _pyside and _pyside2 functions. First, it's quite unconventional to define a class inside a function, but it will inherit QtUiTools.QUiLoader from PySide/PySide2 and will throw an error if Qt.py is using PyQt4/PyQt5.

Right now, I'm just putting the class definition in both these functions. Any idea on how we could structure this more nicely?

[fredrikaverpil]

Never mind, I think I found a solution.